These types of fleece layers have been known for a long time and are usually designed as in-phase layers, in which an upper carriage and a laying carriage each move back and forth in the same rhythm and in the same direction. Two card web conveyor belts are used to transport the card web to the laying nip in the laying carriage, wherein, in an area between the upper carriage and the laying carriage, the card web is sandwiched between two sections of the two card web conveyor belts. This ensures that the card web is guided securely to the laying nip. So that the fleece laid on the output conveyor belt will not be subjected to eddying (i.e. displacements, irregularities, etc.) caused by air eddies, the lower sections of the card web conveyor belts serve simultaneously as cover belts, which cover the laid fleece. Examples of fleece-laying machines are known from U.S. Pat. No. 4,830,351 and EP 0 522 893 A. A specially designed embodiment of a fleece layer is known from EP 1 816 243 A1.
During the transport of the card web through the fleece layer, the high belt speeds cause problems with belt guidance in the area of the lower strands of the belts which function as cover belts. This is especially true in the case of very wide fleece layers such as papermaker felt layers. This lack of guidance has the undesirable side effect that, as a result of the upward and downward movement of the sections of the card web conveyor belts functioning as cover belts, the fleece which has already been laid on the output conveyor belt is subjected to considerable air turbulence and thus to eddying.
To avoid the oscillation of the lower sections of the card web conveyor belts, a support carriage is provided in EP 1 010 787 B1. This carriage is located on the side of the laying carriage facing away from the upper carriage, and it supports the lower strand of the card web conveyor belt traveling on this side. The support carriage can be moved at the speed of the upper carriage and is especially helpful when the laying carriage is close to the upper carriage, because then the distance bridged by the lower strand of the card web conveyor belt to be supported is especially long.
In a similar manner, it is known from EP 1 010 786 B1 that a support carriage for the lower strand of the other card web conveyor belt can be rigidly connected to the upper carriage. It is especially useful in situations in which the laying carriage and the upper carriage are a considerable distance away from each other.
It has been found, however, that, especially in cases where the web is laid over a very wide output belt, the oscillations of the cover belts still subject the card web to eddying, and thus the uniformity of the laid fleece still leaves something to be desired.